Common sizes include letter-size (8½" x 11") and larger booklet-envelope formats. Examples shown in listings are about 9.75 x 13 inches and 11.5 x 9.5 inches, and many items explicitly state they hold letter-size sheets.
These items are typically made from plastic—most often polypropylene. Expanding files and folders in listings are consistently described as plastic or polypropylene construction.
Closures vary by style: some poly envelopes use zipper/zip closures, accordion files commonly use string-and-button closures, and several expanding files use bungee-cord or tuck-away flap styles to secure contents.
Some plastic folders are designed for binder compatibility or loose-page retention. Examples include 3-ring hole-punch folders and folders described with prongs to hold loose pages.
Descriptions commonly highlight durable, reinforced plastic construction and explicitly state water-resistant or water-and-tear resistance. User reviews frequently describe certain folders as durable and long-lasting.
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